The invention relates to novel oxidation dye precursors and to agents for coloring keratin-containing fibers, particularly human hair, that contain these compounds.
In the field of traditional hair dyeing, oxidation dyes have attained substantial importance. The color in this case is created by reaction of certain developers with certain couplers in the presence of an oxidant. Of particular importance are hair colorants for coloring in the natural shade range. By a suitable combination of developers and couplers, trendy shades can also be attained.
Dyes intended for dyeing human hair are subject to special requirements. On the one hand, such dyes must give colorations of the desired shade and intensity and, on the other, they must be toxicologically and dermatologically harmless and non-sensitizing.
The requirements placed on dyes intended for achieving trendy color shades can be significantly different from those placed on dyes for covering the natural shade range. A primary criterion is, for example, the purity of the dye, which is reflected in the brilliance of the resulting color. In the blue range, in particular, no combinations have thus far been found which, together with the often used p-phenylenediamines [for example p-phenylenediamine, p-toluylenediamine and 2,5-diamino-(2′-hydroxyethyl)benzene] would make it possible to obtain very pure blue shades. Common blue couplers, for example 2,4-diaminophenoxyethanol, 5-[(2-hydroxyethyl)amino]-2-meth-oxyaniline or 1,3-di(2,4-diami-nophenoxy)propane, cannot produce brilliant blue shades, because they give rise to a considerable red content. In the L*a*b*color system, this red content is indicated by increased a* values.